Add STEMMA amp code.

Author: kattni

Adafruit_STEMMA_Audio_Amp/Arduino/PWMAudio_Mono_RP2040/.qt_py_rp2040.test.only

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+/*
+  This example plays a tune through a mono amplifier using a simple sine wave.
+
+  Released to the public domain by Earle F. Philhower, III <earlephilhower@yahoo.com>
+
+  Adapted from stereo original example 2023 by Kattni Rembor
+*/
+
+#include <PWMAudio.h>
+
+PWMAudio pwm(0, true); // GP0 = left, GP1 = right
+
+const int freq = 48000; // Output frequency for PWM
+
+int16_t mono = 0;
+
+const int notes[] = { 784, 880, 698, 349, 523 };
+const int dly[] =   { 400, 500, 700, 500, 1000 };
+const int noteCnt = sizeof(notes) / sizeof(notes[0]);
+
+int freqMono = 1;
+
+double sineTable[128]; // Precompute sine wave in 128 steps
+
+unsigned int cnt = 0;
+void cb() {
+  while (pwm.availableForWrite()) {
+    double now = ((double)cnt) / (double)freq;
+    int freqScale = freqMono << 7; // Prescale by 128 to avoid FP math later on
+    pwm.write((int16_t)(mono * sineTable[(int)(now * freqScale) & 127]));
+    cnt++;
+  }
+}
+
+void setup() {
+  // Set up sine table for waveform generation
+  for (int i = 0; i < 128; i++) {
+    sineTable[i] = sin(i * 2.0 * 3.14159 / 128.0);
+  }
+  pwm.setBuffers(4, 32); // Give larger buffers since we're are 48khz sample rate
+  pwm.onTransmit(cb);
+  pwm.begin(freq);
+}
+
+void loop() {
+  delay(1000);
+  mono = 0;
+  Serial.println("loop");
+  for (int i = 0; i < noteCnt; i++) {
+    freqMono = notes[i];
+    mono = 5000;
+    delay(dly[i]);
+  }
+  mono = 0;
+  delay(3000);
+}

Adafruit_STEMMA_Audio_Amp/Arduino/PWMAudio_Mono_RP2040/PWMAudio_Mono_RP2040.ino

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+# SPDX-FileCopyrightText: 2023 Kattni Rembor for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+"""
+CircuitPython PWM Audio Short Tone Tune Demo
+
+Plays a five-note tune on a loop.
+"""
+import time
+import array
+import math
+import board
+from audiocore import RawSample
+from audiopwmio import PWMAudioOut as AudioOut
+
+# Increase this to increase the volume of the tone.
+tone_volume = 0.1
+# The tones are provided as a frequency in Hz. You can change the current tones or
+# add your own to make a new tune. Follow the format with commas between values.
+tone_frequency = [784, 880, 698, 349, 523]
+
+audio = AudioOut(board.A0)
+
+while True:
+    # Play each tone in succession.
+    for frequency in tone_frequency:
+        # Compute the sine wave for the current frequency.
+        length = 8000 // frequency
+        sine_wave = array.array("H", [0] * length)
+        for index in range(length):
+            sine_wave[index] = int((1 + math.sin(math.pi * 2 * index / length))
+                                   * tone_volume * (2 ** 15 - 1))
+
+        sine_wave_sample = RawSample(sine_wave)
+
+        # Play the current frequency.
+        audio.play(sine_wave_sample, loop=True)
+        time.sleep(0.5)
+        audio.stop()
+        time.sleep(1)
+
+    # All done playing all tones; start over from the beginning.